DESCRIPTION: Aim 1 is to further define how XKCM1 destabilizes microtubules by a series of domain studies. A second series of studies will be focused on establishing evolutionary conservation of the microtubule destabilizing activity of other KinI family members. Aim 2 is to identify and characterize proteins that interact with XKCM1. Here the applicant is particularly interested in identifying potential kinetochore components involved in association of XKCM1 with chromosomes. Aim 3 is to investigate the mechanism of chromosome segregation in Xenopus extracts. Aim 4 is to use reagents, developed in previous studies, to disrupt XKCMP1 function in vivo. Aim 5 is to assess chromosome movement in cells where XKCMP1 function has been manipulated as in the previous aim.